FTA on echostar 7 - interesting

[determined]

Just for fun I decided to go to echostar 7 and see if I could get any of the DISH programming marked as free on Lyngsat. Since they use circular polarization I figured I'd get nothing as I only have linear feeds. To my surprise I was able to tune everything marked as free. The dish position was more sensitive than Ku band usually is, but I got signals around 88 to 92 as indicated by my Coolsat for everything. The other interesting thing is that the skew didn't seem to make any difference on some channels but it was important on others. I haven't researched circular polarization except in only the most general way, so I guess I really don't know much about it technically.

 

[Mr Tony]

Are you using a circular LNB (like a DBS LNB or the Invacom?). I know of some times where you can get circular polarity with a linear but the signal is very low

Circular polarity doesnt need to be skewed. No matter what way you have the LNB turned, you'll get the same signal strength

 

[determined]

Are you using a circular LNB (like a DBS LNB or the Invacom?). I know of some times where you can get circular polarity with a linear but the signal is very low

Circular polarity doesnt need to be skewed. No matter what way you have the LNB turned, you'll get the same signal strength

I'm using a corotor feed horn (very much like a Chaparral corotor) with a Norsat 4206A LNB on the Ku side. The C-band LNB is old and I don't remember what it is. Maybe the 10 foot dish boosts the signal enough to get a good signal even though I don't have any circular equipment. I was able to get NASA and Angel 1 TV and a lot of music channels. There was also a test channel in the clear and a couple of other set up types. You are right about the skew. It didn't seem to matter where I put it for most of the music but some channels needed to be set specifically. Angel 1 and NASA needed to be set specifically and different from the music. I just thought it was interesting, but people tell me that I'm easy to keep occupied. By the way, a servo motor on the corotor turns a little bent wire inside the feed horn to adjust the skew, and I control it from my 920, so the LNB never moves.

 

[PhilipPeake]

A linear LNB with a circularly polarised signal will receive a signal 3db lower than you would get with a correctly polarised LNB (half the power).

From a high power satellite such as the DBS satellites, there is a good chance of getting a usable signal.

There are two things to watch for: You WILL have problems if the transponder transmits two signals with the opposite (circular) polarization on the same frequency -- your linear LNB will receive both at equal strength and they will interfere with each other badly. Secondly, unless you are directly under the satellite, the signal you receive is likely to be more eliptical than circular. What this means in pracice is that although with true circular polarization skewing a linear LNB will make zero difference, if the signal is eliptical rather than circular, you will see a difference as you skew the LNB.

If you really want to receive these signals, the best advice is to get a circular LNB to use with them.

 

[determined]

A linear LNB with a circularly polarised signal will receive a signal 3db lower than you would get with a correctly polarised LNB (half the power).

From a high power satellite such as the DBS satellites, there is a good chance of getting a usable signal.

There are two things to watch for: You WILL have problems if the transponder transmits two signals with the opposite (circular) polarization on the same frequency -- your linear LNB will receive both at equal strength and they will interfere with each other badly. Secondly, unless you are directly under the satellite, the signal you receive is likely to be more eliptical than circular. What this means in pracice is that although with true circular polarization skewing a linear LNB will make zero difference, if the signal is eliptical rather than circular, you will see a difference as you skew the LNB.

If you really want to receive these signals, the best advice is to get a circular LNB to use with them.

Thanks for the information. What you explained could be what I was seeing. I'm not really interested in that bird as I can get all the channels of interest on it elsewhere on FTA or C/Ku analog and 4DTV. It was just an experiment to see what would happen. Your explanation makes sense. Thanks again.